Currently, power failure protection on a disk array (RAID, Redundant Array of Independent Disks)/solid state disk (SSD, Solid-State Disk) card is implemented mainly by using “a Nand flash+a supercapacitor/battery”. That is, when a primary power supply fails, the supercapacitor/battery, due to its discharging capability, may serve as a backup battery to supply backup power, and save data in a Cache into the Nand flash or another storage medium on which data loss does not occur in the case of power failure.
For example, it is assumed that a working voltage of the supercapacitor is fixed at a voltage value U1, where the U1 needs to last a power failure protection time when a service volume is maximum. Further referring to FIG. 1, FIG. 1 is a schematic diagram showing comparison of a working voltage of the supercapacitor with a discharging capability of the supercapacitor in an existing solution; as shown in the figure, because voltage stress always exists on the supercapacitor, a service life of the supercapacitor is significantly affected, and a larger working voltage results in faster aging of the supercapacitor.